Butterflies change travel plans as U.K. warms

British winters used to be too cold for the butterflies, but not anymore.

Is the United Kingdom about to be colonized? Last month Butterfly Conservation revealed that a dozen adult continental swallowtail butterflies had been observed on the U.K.'s south coast. Now, a dozen butterflies may not seem like much, but the fact that the insects successfully survived the normally cold British winter is a sign that the region is warming enough to make it more hospitable to the species, which is normally found across the English Channel in France.

The continental swallowtail, which is larger than the U.K.'s native swallowtail species, is described as a tropical butterfly more acclimated to warmer climates.

Michael Blencowe from Butterfly Conservation's Sussex Branch said in a news release last month that the organization's volunteers observed six of the 12 adults emerge from pupae. Adult swallowtails typically come to the U.K. from France during the summer but don't survive the winter. Last summer was abnormally warm and saw was Butterfly Conservation called "the largest continental Swallowtail invasion since 1945." The hot summer was followed by a mild winter, allowing the pupae to survive.

Beyond the initial 12 adults that emerged this year, Blencowe speculated that "There are still more to emerge and no doubt many other swallowtails that we don't know about are roaming the country. This current invasion could be the start of the colonization of Southern England by the swallowtail. In 20 years this butterfly could be a regular visitor to our gardens."

This isn't the only species making its way to warmer Britain. The Telegraph recently ran a slideshow of other butterflies and moths taking advantage of climate change, including the long-tailed blue butterfly, which saw record numbers last year; the large Clifden nonpareil moth, which has been spotted several times in three towns; the rosy underwing, which until this year had only been seen 10 times in the U.K.; and the crimson speckled moth, which is making its way up from northern Africa.

Meanwhile, Britain's native butterflies are also changing their habitat due to climate change, and not always for the better. The U.K.'s own swallowtail, for instance, is now restricted to a small range in Norfolk Broads. A 2001 paper in Nature predicted this after documenting "rapid responses" to climate change and habitat loss in 46 species of butterflies.

The situation isn't unique to the United Kingdom. In the U.S., a butterfly called the quino checkerspot has shifted its habitat in California and Mexico to higher altitudes. In doing so, it has chosen a different type of plant on which to lay its eggs. The unexpected and unprecedented move could save the species from extinction.